1. Field of the Invention
The present invention relates generally to brakes for vehicles, and more particularly, to an improved brake employing inner and outer brakes shoes to grip inner and outer braking surfaces on a rotatable drum.
2. Prior Art
A number of proposals have been made in the prior art to employ inner and outer brake shoes operating concurrently on the inner and outer surfaces of a cylindrical brake drum. One such proposal is presented in U.S. Pat. No. 2,783,858 issued Mar. 5, 1957 to John H. Murphy.
One drawback of most of these proposals is that the freedom of movement of the brake shoes is restricted, typically to a pivotal motion. This restricted mounting does not permit the shoes to "float" or self-align with the drum when braking engagement is initiated. If the brake drum is warped from heat or out of warpage, the restricted mounting can reduce the area of braking engagement between the drum and the shoes, can cause undue and uneven wear on the brake shoes an drums, and can diminish the effective operating life of the shoes and the drum.
Another disadvantage of prior art proposals which pin or otherwise securely connect the brake shoes to a stationary mount is that these connections complicate assembly and disassembly of the brake. The connections add to the cost of the brake and provide additional areas which are subject to wear.
Still another disadvantage of prior brake proposals is that they include a relatively large number of parts, many if not most of which must be accurately formed and machined. Some of these parts must be made with close tollerances to assure their proper operation, and this adds significantly to the cost of the assembled brake.